1. Technical Field
The present invention relates to a pressure sensor package having a pressure inlet pipe, and in particular, relates to a pressure sensor package that can prevent a blocking of a hole of the pressure inlet pipe due to the condensation of a pressure medium.
2. Related Art
Pressure sensors are widely used in automobiles, and are used in conditions of severe heat and cold. For example, they may be installed in an engine compartment, used as a manifold pressure sensor, or installed as an exhaust gas filter clogging sensor. In this way, they are used where there is a considerable change in the temperature of a measurement medium (air or exhaust gas) itself, or in the temperature of a product in an environment in which the sensor is installed.
FIGS. 15A and 15B are configuration diagrams of a pressure sensor package, wherein FIG. 15A is a main portion plan view, and FIG. 15B is a main portion sectional view cut along an X-X line of FIG. 15A.
FIGS. 16A and 16B are configuration diagrams of a pressure inlet pipe, wherein FIG. 16A is a main portion side sectional view of a B portion of FIG. 15B, and FIG. 16B is a main portion plan view cut along an X-X line of FIG. 16A.
A pressure sensor package 500 is formed of a case 51, a cover 52, and a pressure inlet pipe 53. A pressure sensor chip 61 and an external lead terminal 62 connected to the chip 61 are housed in the case 51. The whole is a heretofore known pressure sensor.
A hole 54 of the pressure inlet pipe 53 reaches the pressure sensor chip 61, and the pressure of a pressure medium (air or the like) introduced into the hole 54 of the pressure inlet pipe 53 is detected and measured by the pressure sensor chip 61.
A description will be given of a method of processing the hole 54 of the pressure inlet pipe 53. For example, when the pressure inlet pipe 53 is metallic, there is a grinding processing, an extrusion processing, a drawing processing, a casting, a pressing, and the like. Also, when the pressure inlet pipe 53 is of a resin, it is processed by a resin molding. The hole 54 of the pressure inlet pipe 53 is circular, and the machined surface of the hole 54 is finished comparatively smoothly to a roughness in the order of a few micrometers.
In JP-A-2008-122182, a description is given of a pressure sensor device, or more specifically of a pressure sensor container of the device, including a pressure detection chamber into which a gas whose pressure is to be measured is introduced, a pressure sensor element that detects the pressure of the gas, and a protective wall that prevents a foreign object from entering the pressure detection chamber.
The protective wall includes an inclined surface, and the inclined surface is given an angle θ8 a such that, when the pressure sensor device is disposed inclined at a first angle θ1 with respect to the horizontal, a second angle θ2 is held facing downward between the inclined surface and the horizontal.
Also, it is described that, by forming a separate inclined surface as necessary in the inner peripheral wall of the pressure detection chamber, it is possible, even when the pressure sensor device is disposed inclined due to a layout, or the like, to provide a pressure sensor device and pressure sensor container with which it is possible to prevent a freezing of moisture, a swelling of a gel-form coating member, and pressure sensor element damage, without allowing moisture, oil, gasoline, or the like, to accumulate on the protective wall.
With the heretofore known pressure inlet pipe 53, when the introduced pressure medium, such as air, reaches a low temperature, it may happen that condensation forms on a wall surface 55 of the hole 54 of the pressure inlet pipe 53.
FIGS. 17A and 17B and FIGS. 18A and 18B are diagrams showing a condensation condition, wherein FIGS. 17A and 17B are diagrams showing an initial condition, and FIGS. 18A and 18B are diagrams showing a late stage condensation condition. In the drawings, FIGS. 17A and 18A are side sectional views, and FIGS. 17B and 18B are main portion plan views cut along an X-X line of FIGS. 17A and 18A respectively.
As the pressure medium, there is air, a vapor of gasoline or oil, a combustible gas, or the like. Also, the pressure medium condensed and forming a spherical liquid is called a droplet 63a. 
As shown in FIG. 17A, the pressure medium condenses, becoming the droplet 63, and the droplet 63 becomes spherical due to surface tension and leakage. Next, as shown in FIG. 18B, when growth of the condensed droplet 63 advances further due to condensation, the droplet 63 blocks the hole 54 of the pressure inlet pipe 53. However, as the droplet 63 moves under the pressure of the pressure medium in this condition, there is no impediment to the detection and measurement of the pressure of the pressure medium.
However, when the condensed droplet 63 is exposed to low temperature and solidifies, the droplet 63 blocking the hole 54 of the pressure inlet pipe 53 solidifies, and becomes a solid (for example, it freezes). As a result of this, as the hole 54 of the pressure inlet pipe 53 is completely blocked by the solid, and the solid does not move under the pressure of the pressure medium, it is not possible to communicate the pressure of the pressure medium to the pressure sensor chip 61. Because of this, for example, it is not possible to operate an automobile engine system normally.
In order to prevent the hole 54 of the pressure inlet pipe 53 from being blocked as heretofore described, there is a method whereby the diameter of the hole 54 is increased, but when increasing the size of the hole 54, the external form of the pressure sensor package 500 increases in size, and the manufacturing cost also increases.
Also, in JP-A-2008-122182, there is no description of a formation of a groove in the wall surface of the hole of the pressure inlet pipe in order to prevent the pressure inlet pipe being completely blocked by the pressure medium condensing and the droplet solidifying.